Define returns_state in capabilities

CHANGELOG.md

@@ -10,10 +10,16 @@
 
 ### Bug fixes
 
+* Defines the missing `returns_state` entry of the
+  `capabilities` dictionary for devices.
+  [(#107)](https://github.com/PennyLaneAI/pennylane-cirq/pull/107)
+
 ### Contributors
 
 This release contains contributions from (in alphabetical order):
 
+Antal Száva
+
 ---
 
 # Release 0.22.0

doc/requirements.txt

@@ -2,7 +2,7 @@ alabaster==0.7.12
 appdirs==1.4.4
 attrs==20.3.0
 autograd==1.4
-autoray==0.2.5
+autoray==0.3.1
 backports.cached-property==1.0.1
 Babel==2.9.1
 cachetools==4.2.4
@@ -41,7 +41,7 @@ openfermion==1.3.0
 openfermionpyscf==0.5
 packaging==21.0
 pandas==1.3.5
-git+https://github.com/XanaduAI/pennylane.git#egg=pennylane
+pennylane==0.23.0
 PennyLane-Lightning==0.23
 Pillow==9.1.0
 pluggy==1.0.0
@@ -77,4 +77,4 @@ tqdm==4.64.0
 traitlets==5.1.0
 typing_extensions==3.10.0.0
 urllib3==1.26.9
-zipp==3.8.0
+zipp==3.8.0

pennylane_cirq/qsim_device.py

@@ -75,9 +75,11 @@ def operations(self):
         }
         return ops
 
-    @classmethod
-    def capabilities(cls):
+    def capabilities(self):
         # pylint: disable=missing-function-docstring
+
+        # Note: this is an instance method as parent's capabilities is an
+        # instance method too
         capabilities = super().capabilities().copy()
         capabilities.update(
             supports_inverse_operations=False,
@@ -135,11 +137,10 @@ def operations(self):
         }
         return ops
 
-    @classmethod
-    def capabilities(cls):
-        # pylint: disable=missing-function-docstring
+    def capabilities(self):  # pylint: disable=missing-function-docstring
         capabilities = super().capabilities().copy()
         capabilities.update(
+            returns_state=(self.shots is None),  # State information is only set if obtaining shots
             supports_inverse_operations=False,
         )
         return capabilities

pennylane_cirq/simulator_device.py

@@ -78,6 +78,13 @@ def reset(self):
         self._result = None
         self._state = None
 
+    def capabilities(self):  # pylint: disable=missing-function-docstring
+        capabilities = super().capabilities().copy()
+        capabilities.update(
+            returns_state=(self.shots is None)  # State information is only set if obtaining shots
+        )
+        return capabilities
+
     def _apply_basis_state(self, basis_state_operation):
         # pylint: disable=missing-function-docstring
         if not self.shots is None:
@@ -297,6 +304,13 @@ def __init__(self, wires, shots=None, qubits=None):
         self._result = None
         self._state = None
 
+    def capabilities(self):  # pylint: disable=missing-function-docstring
+        capabilities = super().capabilities().copy()
+        capabilities.update(
+            returns_state=(self.shots is None)  # State information is only set if obtaining shots
+        )
+        return capabilities
+
     def expval(self, observable, shot_range=None, bin_size=None):
         # The simulate_expectation_values from Cirq for mixed states involves
         # a density matrix check, which does not always pass because the tolerance

requirements-ci.txt

@@ -1,4 +1,4 @@
-pennylane
+git+https://github.com/PennyLaneAI/pennylane.git
 cirq-core
 cirq-pasqal
-numpy
+numpy

requirements.txt

@@ -1,6 +1,6 @@
 appdirs==1.4.4
 autograd==1.4
-autoray==0.2.5
+autoray==0.3.1
 cachetools==5.0.0
 certifi==2021.10.8
 charset-normalizer==2.0.12
@@ -28,7 +28,7 @@ openfermion==1.1.0
 openfermionpyscf==0.5
 packaging==21.0
 pandas==1.3.3
-git+https://github.com/XanaduAI/pennylane.git#egg=pennylane
+pennylane==0.23.0
 PennyLane-Lightning==0.22.1
 Pillow==9.1.0
 pluggy==1.0.0